It’s quite inevitable, really: after Google announced free turn-by-turn GPS navigation for Android devices, followed by Nokia’s decision to offer the same on its smartphones, the price of full-featured GPS navigation apps on other platforms is hurling towards zero.

Case in point: MapQuest 4 Mobile, a free GPS navigation app for the iPhone, now offers “basic voice guidance.”

The app will tell you when you need to take a turn, and if you get lost, it will warn you that you’re off route.Other features include saving maps and routes on MapQuest.com and retrieving them on your iPhone, easy POI finding via the OS X dashboard-like Place Carousel, finding you on a map or in relation to a route, and free form search.

The app is available for free in Apple’s App Store.

On Tuesday Yahoo introduced two new search iPhone applications at the C.T.I.A. conference in Las Vegas.

One of the apps, called Yahoo Search iPhone App, is an integrated search service for the Apple iPhone and includes a number of interesting features, including voice search and “Shake to Clear,” which does exactly what the name describes: clears the last search when you shake the phone.

The new app also offers a range of new local tools and features  that can refine a Yahoo search based on a user’s current location and also add relevant maps using location-aware technology.

The other new iPhone application is called Yahoo Sketch-a-Search.

The service works by allowing users to draw a boundary on a map around a specific location. The app will then bring up local content, including restaurants and businesses, without a user needing to know the name of an area or neighborhood. In addition, the app also filters restaurant results by cuisine, ambiance and star rating, Yahoo said.

The release of these new applications and other recent mobile content shows Yahoo’s continued efforts to stay involved in the growing mobile space.

In the early days of the Internet on cellphones, Yahoo was considered a thought leader, releasing numerous mobile applications around news, search, mail, and chat. Over the last several years, Yahoo’s competitors have quickly surpassed the company by releasing handsets, operating systems and entire ecosystems around devices.